Bats are mammaws of de orderChiroptera;[a] wif deir forewimbs adapted as wings, dey are de onwy mammaws capabwe of true and sustained fwight. Bats are more manoeuvrabwe dan birds, fwying wif deir very wong spread-out digits covered wif a din membrane or patagium. The smawwest bat, and arguabwy de smawwest extant mammaw, is Kitti's hog-nosed bat, which is 29–34 miwwimetres (11⁄8–13⁄8 inches) in wengf, 150 mm (6 in) across de wings and 2–2.6 g (1⁄16–3⁄32 oz) in mass. The wargest bats are de fwying foxes and de giant gowden-crowned fwying fox, Acerodon jubatus, which can weigh 1.6 kg (31⁄2 wb) and have a wingspan of 1.7 m (5 ft 7 in).

The second wargest order of mammaws after rodents, bats comprise about 20% of aww cwassified mammaw species worwdwide, wif over 1,200 species. These were traditionawwy divided into two suborders: de wargewy fruit-eating megabats, and de echowocatingmicrobats. But more recent evidence has supported dividing de order into Yinpterochiroptera and Yangochiroptera, wif megabats as members of de former awong wif severaw species of microbats. Many bats are insectivores, and most of de rest are frugivores (fruit-eaters). A few species feed on animaws oder dan insects; for exampwe, de vampire batsfeed on bwood. Most bats are nocturnaw, and many roost in caves or oder refuges; it is uncertain wheder bats have dese behaviours to escape predators. Bats are present droughout de worwd, wif de exception of extremewy cowd regions. They are important in deir ecosystems for powwinatingfwowers and dispersing seeds; many tropicaw pwants depend entirewy on bats for dese services.

Bats provide humans wif some benefits, at de cost of some dreats. Bat dung has been mined as guano from caves and used as fertiwiser. Bats consume insect pests, reducing de need for pesticides. They are sometimes numerous enough to serve as tourist attractions, and are used as food across Asia and de Pacific Rim. They are naturaw reservoirs of many padogens, such as rabies; and since dey are highwy mobiwe, sociaw, and wong-wived, dey can readiwy spread disease. In many cuwtures, bats are popuwarwy associated wif darkness, mawevowence, witchcraft, vampires, and deaf.

Etymowogy

An owder Engwish name for bats is fwittermouse, which matches deir name in oder Germanic wanguages (for exampwe German Fwedermaus and Swedish fwaddermus), rewated to de fwuttering of wings. Middwe Engwish had bakke, most wikewy cognate wif Owd Swedish natbakka ("night-bat"), which may have undergone a shift from -k- to -t- (to Modern Engwish bat) infwuenced by Latin bwatta, "mof, nocturnaw insect". The word "bat" was probabwy first used in de earwy 1570s.[2][3] The name "Chiroptera" derives from Ancient Greek: χείρ – cheir, "hand"[4] and πτερόν – pteron, "wing".[1][5]

Phywogeny and taxonomy

Evowution

The dewicate skewetons of bats do not fossiwise weww, and it is estimated dat onwy 12% of bat genera dat wived have been found in de fossiw record.[6] Most of de owdest known bat fossiws were awready very simiwar to modern microbats, such as Archaeopteropus (32 miwwion years ago).[7] The extinct bats Pawaeochiropteryx tupaiodon (48 miwwion years ago) and Hassianycteris kumari (55 miwwion years ago) are de first fossiw mammaws whose cowouration has been discovered: bof were reddish-brown, uh-hah-hah-hah.[8][9]

The phywogenetic rewationships of de different groups of bats have been de subject of much debate. The traditionaw subdivision into Megachiroptera and Microchiroptera refwected de view dat dese groups of bats had evowved independentwy of each oder for a wong time, from a common ancestor awready capabwe of fwight. This hypodesis recognised differences between microbats and megabats and acknowwedged dat fwight has evowved onwy once in mammaws. Most mowecuwar biowogicaw evidence supports de view dat bats form a naturaw or monophywetic group.[7]

In de 1980s, a hypodesis based on morphowogicaw evidence stated de Megachiroptera evowved fwight separatewy from de Microchiroptera. The fwying primate hypodesis proposed dat, when adaptations to fwight are removed, de Megachiroptera are awwied to primates by anatomicaw features not shared wif Microchiroptera. For exampwe, de brains of megabats have advanced characteristics. Awdough recent genetic studies strongwy support de monophywy of bats,[7] debate continues about de meaning of de genetic and morphowogicaw evidence.[19]

The 2003 discovery of an earwy fossiw bat from de 52-miwwion-year-owd Green River Formation, Onychonycteris finneyi, indicates dat fwight evowved before echowocative abiwities.[20][21]Onychonycteris had cwaws on aww five of its fingers, whereas modern bats have at most two cwaws on two digits of each hand. It awso had wonger hind wegs and shorter forearms, simiwar to cwimbing mammaws dat hang under branches, such as swods and gibbons. This pawm-sized bat had short, broad wings, suggesting dat it couwd not fwy as fast or as far as water bat species. Instead of fwapping its wings continuouswy whiwe fwying, Onychonycteris probabwy awternated between fwaps and gwides in de air.[7] This suggests dat dis bat did not fwy as much as modern bats, but fwew from tree to tree and spent most of its time cwimbing or hanging on branches.[22] The distinctive features of de Onychonycteris fossiw awso support de hypodesis dat mammawian fwight most wikewy evowved in arboreaw wocomotors, rader dan terrestriaw runners. This modew of fwight devewopment, commonwy known as de "trees-down" deory, howds dat bats first fwew by taking advantage of height and gravity to drop down on to prey, rader dan running fast enough for a ground-wevew take off.[23][24]

The mowecuwar phywogeny was controversiaw, as it pointed to microbats not having a uniqwe common ancestry, which impwied dat some seemingwy unwikewy transformations occurred. The first is dat waryngeaw echowocation evowved twice in bats, once in Yangochiroptera and once in de rhinowophoids.[25] The second is dat waryngeaw echowocation had a singwe origin in Chiroptera, was subseqwentwy wost in de famiwy Pteropodidae (aww megabats), and water evowved as a system of tongue-cwicking in de genus Rousettus.[26] Anawyses of de seqwence of de vocawization gene FoxP2 were inconcwusive on wheder waryngeaw echowocation was wost in de pteropodids or gained in de echowocating wineages.[27] Echowocation probabwy first derived in bats from communicative cawws. The Eocene bats Icaronycteris (52 miwwion years ago) and Pawaeochiropteryx had craniaw adaptations suggesting an abiwity to detect uwtrasound. This may have been used at first mainwy to forage on de ground for insects and map out deir surroundings in deir gwiding phase, or for communicative purposes. After de adaptation of fwight was estabwished, it may have been refined to target fwying prey by echowocation, uh-hah-hah-hah.[22] Bats may have evowved echowocation drough a shared common ancestor, in which case it was den wost in de Owd Worwd megabats, onwy to be regained in de horseshoe bats; or, echowocation evowved independentwy in bof de Yinpterochiroptera and Yangochiroptera wineages.[28] Anawyses of de hearing gene Prestin seem to favour de idea dat echowocation devewoped independentwy at weast twice, rader dan being wost secondariwy in de pteropodids,[29] but ontogenic anawysis of de cochwea supports dat waryngeaw echowocation evowved onwy once.[30]

Cwassification

Bats are pwacentaw mammaws. After rodents, dey are de wargest order, making up about 20% of mammaw species.[31] In 1758, Carw Linnaeus cwassified de seven bat species he knew of in de genus Vespertiwio in de order Primates. Around twenty years water, de German naturawist Johann Friedrich Bwumenbach gave dem deir own order, Chiroptera.[32] Since den, de number of described species has risen to over 1,200, traditionawwy cwassified as two suborders: Megachiroptera (megabats), and Microchiroptera (microbats/echowocating bats).[33] Not aww megabats are warger dan microbats.[34] Severaw characteristics distinguish de two groups. Microbats use echowocation for navigation and finding prey, but megabats apart from dose in de genus Rousettus do not, rewying instead on deir eyesight.[35] Accordingwy, megabats have a weww-devewoped visuaw cortex and good visuaw acuity.[33] Megabats have a cwaw on de second finger of de forewimb.[36][37] The externaw ears of microbats do not cwose to form a ring; de edges are separated from each oder at de base of de ear.[37] Megabats eat fruit, nectar, or powwen, whiwe most microbats eat insects; oders feed on fruit, nectar, powwen, fish, frogs, smaww mammaws, or bwood.[33]

Anatomy and physiowogy

Skuww and dentition

A preserved megabat showing how de skeweton fits inside its skin

The head and teef shape of bats can vary by species. In generaw, megabats have wonger snouts, warger eye sockets and smawwer ears, giving dem a more dog-wike appearance, which is de source of deir nickname of "fwying foxes".[39] Among microbats, wonger snouts are associated wif nectar-feeding.[40] whiwe vampire bats have reduced snouts to accommodate warge incisors and canines.[41]

Smaww insect-eating bats can have as many as 38 teef, whiwe vampire bats have onwy 20. Bats dat feed on hard-shewwed insects have fewer but warger teef wif wonger canines and more robust wower jaws dan species dat prey on softer bodied insects. In nectar-feeding bats, de canines are wong whiwe de cheek-teef are reduced. In fruit-eating bats, de cusps of de cheek teef are adapted for crushing.[40] These feeding behaviors are true for bof megabats and microbats. The upper incisors of vampire bats wack enamew, which keeps dem razor-sharp.[41] The bite force of smaww bats is generated drough mechanicaw advantage, awwowing dem to bite drough de hardened armour of insects or de skin of fruit.[42]

The finger bones of bats are much more fwexibwe dan dose of oder mammaws, owing to deir fwattened cross-section and to wow wevews of cawcium near deir tips. The ewongation of bat digits, a key feature reqwired for wing devewopment, is due to de upreguwation of bone morphogenetic proteins (Bmps). During embryonic devewopment, de gene controwwing Bmp signawwing, Bmp2, is subjected to increased expression in bat forewimbs—resuwting in de extension of de manuaw digits. This cruciaw genetic awteration hewps create de speciawised wimbs reqwired for powered fwight. The rewative proportion of extant bat forewimb digits compared wif dose of Eocene fossiw bats have no significant differences, suggesting dat bat wing morphowogy has been conserved for over 50 miwwion years.[45] During fwight, de bones undergo bending and shearingstress; de bending stresses fewt are smawwer dan in terrestriaw mammaws, but de shearing stress is warger. The wing bones of bats have a swightwy wower breaking stress point dan dose of birds.[46]

As in oder mammaws, and unwike in birds, de radius is de main component of de forearm. Bats have five ewongated digits, which aww radiate around de wrist. The dumb points forward and supports de weading edge of de wing, and de oder digits support de tension hewd in de wing membrane. The second and dird digits go awong de wing tip, awwowing de wing to be puwwed forward against aerodynamic drag, widout having to be dick as in pterosaur wings. The fourf and fiff digits go from de wrist to de traiwing edge, and repew de bending force caused by air pushing up against de stiff membrane.[47] Due to deir fwexibwe joints, bats are more manoeuvrabwe and more dexterous dan gwiding mammaws.[48]

The wings of bats are much dinner and consist of more bones dan de wings of birds, awwowing bats to manoeuvre more accuratewy dan de watter, and fwy wif more wift and wess drag.[49] By fowding de wings in toward deir bodies on de upstroke, dey save 35 percent energy during fwight.[50] The membranes are dewicate, tearing easiwy,[51] but can regrow, and smaww tears heaw qwickwy.[51][52] The surface of de wings is eqwipped wif touch-sensitive receptors on smaww bumps cawwed Merkew cewws, awso found on human fingertips. These sensitive areas are different in bats, as each bump has a tiny hair in de centre, making it even more sensitive and awwowing de bat to detect and adapt to changing airfwow; de primary use is to judge de most efficient speed to fwy at, and possibwy awso to avoid stawws.[53] Insectivorous bats may awso use tactiwe hairs to hewp perform compwex manoeuvres to capture prey in fwight.[48]

The patagium is de wing membrane; it is stretched between de arm and finger bones, and down de side of de body to de hind wimbs and taiw. This skin membrane consists of connective tissue, ewastic fibres, nerves, muscwes, and bwood vessews. The muscwes keep de membrane taut during fwight.[54] The extent to which de taiw of a bat is attached to a patagium can vary by species, wif some having compwetewy free taiws or even no taiws.[40] The skin on de body of de bat, which has one wayer of epidermis and dermis, as weww as hair fowwicwes, sweat gwands and a fatty subcutaneous wayer, is very different from de skin of de wing membrane. The patagium is an extremewy din doubwe wayer of epidermis; dese wayers are separated by a connective tissue centre, rich wif cowwagen and ewastic fibres. The membrane has no hair fowwicwes or sweat gwands, except between de fingers.[53][55] For bat embryos, apoptosis (ceww deaf) affects onwy de hindwimbs, whiwe de forewimbs retain webbing between de digits dat forms into de wing membranes.[56] Unwike birds, whose stiff wings dewiver bending and torsionaw stress to de shouwders, bats have a fwexibwe wing membrane dat can onwy resist tension, uh-hah-hah-hah. To achieve fwight, a bat exerts force inwards at de points where de membrane meets de skeweton, so dat an opposing force bawances it on de wing edges perpendicuwar to de wing surface. This adaptation does not permit bats to reduce deir wingspans, unwike birds, which can partwy fowd deir wings in fwight, radicawwy reducing de wing span and area for de upstroke and for gwiding. Hence bats cannot travew over wong distances as birds can, uh-hah-hah-hah.[47]

Nectar- and powwen-eating bats can hover, in a simiwar way to hummingbirds. The sharp weading edges of de wings can create vortices, which provide wift. The vortex may be stabiwised by de animaw changing its wing curvatures.[57]

Roosting and gaits

Group of megabats roosting

When not fwying, bats hang upside down from deir feet, a posture known as roosting.[58] The femurs are attached at de hips in a way dat awwows dem to bend outward and upward in fwight. The ankwe joint can fwex to awwow de traiwing edge of de wings to bend downwards. This does not permit many movements oder dan hanging or cwambering up trees.[47] Most megabats roost wif de head tucked towards de bewwy, whereas most microbats roost wif de neck curwed towards de back. This difference is refwected in de structure of de cervicaw or neck vertebrae in de two groups, which are cwearwy distinct.[58] Tendons awwow bats to wock deir feet cwosed when hanging from a roost. Muscuwar power is needed to wet go, but not to grasp a perch or when howding on, uh-hah-hah-hah.[59]

When on de ground, most bats can onwy craww awkwardwy. A few species such as de New Zeawand wesser short-taiwed bat and de common vampire bat are agiwe on de ground. Bof species make wateraw gaits (de wimbs move one after de oder) when moving swowwy but vampire bats move wif a bounding gait (aww wimbs move in unison) at greater speeds, de fowded up wings being used to propew dem forward. Vampire bat wikewy evowved dese gaits to fowwow deir hosts whiwe short-taiwed bats devewoped in de absence of terrestriaw mammaw competitors. Enhanced terrestriaw wocomotion does not appear to have reduced deir abiwity to fwy.[60]

Internaw systems

Bats have an efficient circuwatory system. They seem to make use of particuwarwy strong venomotion, a rhydmic contraction of venous waww muscwes. In most mammaws, de wawws of de veins provide mainwy passive resistance, maintaining deir shape as deoxygenated bwood fwows drough dem, but in bats dey appear to activewy support bwood fwow back to de heart wif dis pumping action, uh-hah-hah-hah.[61][62] Since deir bodies are rewativewy smaww and wightweight, bats are not at risk of bwood fwow rushing to deir heads when roosting.[63]

Bats possess a highwy adapted respiratory system to cope wif de demands of powered fwight, an energeticawwy taxing activity dat reqwires a warge continuous droughput of oxygen, uh-hah-hah-hah. In bats, de rewative awveowar surface area and puwmonary capiwwary bwood vowume are warger dan in most oder smaww qwadrupedaw mammaws.[64] During fwight de respiratory cycwe has a one-to-one rewationship wif de wing-beat cycwe.[65] Because of de restraints of de mammawian wungs, bats cannot maintain high-awtitude fwight.[47]

The wings are highwy vascuwarized membranes, de warger bwood vessews visibwe against de wight.[66]

It takes a wot of energy and an efficient circuwatory system to work de fwight muscwes of bats. Energy suppwy to de muscwes engaged in fwight reqwire about doubwe de amount compared to de muscwes dat do not use fwight as a means of mammawian wocomotion, uh-hah-hah-hah. In parawwew to energy consumption, bwood oxygen wevews of fwying animaws are twice as much as dose of deir terrestriawwy wocomoting mammaws. As de bwood suppwy controws de amount of oxygen suppwied droughout de body, de circuwatory system must respond accordingwy. Therefore, compared to a terrestriaw mammaw of de same rewative size, de bat's heart can be up to dree times warger, and pump more bwood.[67] Cardiac output is directwy derived from heart rate and stroke vowume of de bwood;[68] an active microbat can reach a heart rate of 1000 beats per minute.[69]

Wif its extremewy din membranous tissue, a bat's wing can significantwy contribute to de organism's totaw gas exchange efficiency.[55] Because of de high energy demand of fwight, de bat's body meets dose demands by exchanging gas drough de patagium of de wing. When de bat has its wings spread it awwows for an increase in surface area to vowume ratio. The surface area of de wings is about 85% of de totaw body surface area, suggesting de possibiwity of a usefuw degree of gas exchange.[55] The subcutaneous vessews in de membrane wie very cwose to de surface and awwow for de diffusion of oxygen and carbon dioxide.[70]

The digestive system of bats has varying adaptations depending on de species of bat and its diet. As in oder fwying animaws, food is processed qwickwy and effectivewy to keep up wif de energy demand. Insectivorous bats may have certain digestive enzymes to better process insects, such as chitinase to break down chitin, which is a warge component of insects.[71] Vampire bats, probabwy due to deir diet of bwood, are de onwy vertebrates dat do not have de enzyme mawtase, which breaks down mawt sugar, in deir intestinaw tract. Nectivorous and frugivorous bats have more mawtase and sucrase enzymes dan insectivorous, to cope wif de higher sugar contents of deir diet.[72]

The adaptations of de kidneys of bats vary wif deir diets. Carnivorous and vampire bats consume warge amounts of protein and can output concentrated urine; deir kidneys have a din cortex and wong renaw papiwwae. Frugivorous bats wack dat abiwity and have kidneys adapted for ewectrowyte-retention due to deir wow-ewectrowyte diet; deir kidneys accordingwy have a dick cortex and very short conicaw papiwwae.[72] Bats have higher metabowic rates associated wif fwying, which wead to an increased respiratory water woss. Their warge wings are composed of de highwy vascuwarized membranes, increasing de surface area, and weading to cutaneous evaporative water woss.[66] Water hewps maintain deir ionic bawance in deir bwood, dermoreguwation system, and removaw of wastes and toxins from de body via urine. They are awso susceptibwe to bwood urea poisoning if dey do not receive enough fwuid.[73]

The structure of de uterine system in femawe bats can vary by species, wif some having two uterine horns whiwe oders have a singwe mainwine chamber.[74]

Senses

Echowocation

Microbats and a few megabats emit uwtrasonic sounds to produce echoes. Sound intensity of dese echos are dependent on subgwottic pressure. The bats’ cricodyroid muscwe controws de orientation puwse freqwency, which is an important function, uh-hah-hah-hah. This muscwe is wocated inside de warynx and it is de onwy tensor muscwe capabwe of aiding phonation, uh-hah-hah-hah.[75] By comparing de outgoing puwse wif de returning echoes, de brain and auditory nervous system can produce detaiwed images of de bat's surroundings. This awwows bats to detect, wocawise, and cwassify deir prey in darkness. Bat cawws are some of de woudest airborne animaw sounds, and can range in intensity from 60 to 140 decibews.[76][77] Microbats use deir warynx to create uwtrasound, and emit it drough de mouf and sometimes de nose. The watter is most pronounced in de horseshoe bats (Rhinowophus spp.). Microbat cawws range in freqwency from 14,000 to weww over 100,000 Hz, extending weww beyond de range of human hearing (between 20 and 20,000 Hz).[78] Various groups of bats have evowved fweshy extensions around and above de nostriws, known as nose-weaves, which pway a rowe in sound transmission, uh-hah-hah-hah.[79]

Principwe of bat echowocation: orange is de caww and green is de echo

In wow-duty cycwe echowocation, bats can separate deir cawws and returning echoes by time. They have to time deir short cawws to finish before echoes return, uh-hah-hah-hah. Bats contract deir middwe ear muscwes when emitting a caww, so dey can avoid deafening demsewves. The time intervaw between de caww and echo awwows dem to rewax dese muscwes, so dey can hear de returning echo.[80] The deway of de returning echoes awwows de bat to estimate de range to deir prey.[78]

In high-duty cycwe echowocation, bats emit a continuous caww and separate puwse and echo in freqwency. The ears of dese bats are sharpwy tuned to a specific freqwency range. They emit cawws outside dis range to avoid deafening demsewves. They den receive echoes back at de finewy tuned freqwency range by taking advantage of de Doppwer shift of deir motion in fwight. The Doppwer shift of de returning echoes yiewds information rewating to de motion and wocation of de bat's prey. These bats must deaw wif changes in de Doppwer shift due to changes in deir fwight speed. They have adapted to change deir puwse emission freqwency in rewation to deir fwight speed so echoes stiww return in de optimaw hearing range.[81]

In addition to echowocating prey, bat ears are sensitive to de fwuttering of mof wings, de sounds produced by tymbawate insects, and de movement of ground-dwewwing prey, such as centipedes and earwigs. The compwex geometry of ridges on de inner surface of bat ears hewps to sharpwy focus echowocation signaws, and to passivewy wisten for any oder sound produced by de prey. These ridges can be regarded as de acoustic eqwivawent of a Fresnew wens, and exist in a warge variety of unrewated animaws, such as de aye-aye, wesser gawago, bat-eared fox, mouse wemur, and oders.[82][83][84] Bats can estimate de ewevation of deir target using de interference patterns from de echoes refwecting from de tragus, a fwap of skin in de externaw ear.[78]

By repeated scanning, bats can mentawwy construct an accurate image of de environment in which dey are moving and of deir prey.[87] Some species of mof have expwoited dis, such as de tiger mods, which produces aposematic uwtrasound signaws to warn bats dat dey are chemicawwy protected and derefore distastefuw.[85][86] Mof species incwuding de tiger mof can produce signaws to jam bat echowocation. Many mof species have a hearing organ cawwed a tympanum, which responds to an incoming bat signaw by causing de mof's fwight muscwes to twitch erraticawwy, sending de mof into random evasive manoeuvres.[88][89][90]

Vision

The eyes of most microbat species are smaww and poorwy devewoped, weading to poor visuaw acuity, but no species is bwind.[91] Most microbats have mesopic vision, meaning dat dey can onwy detect wight in wow wevews, whereas oder mammaws have photopic vision, which awwows cowour vision, uh-hah-hah-hah. Microbats may use deir vision for orientation and whiwe travewwing between deir roosting grounds and feeding grounds, as echowocation is onwy effective over short distances. Some species can detect uwtraviowet (UV). As de bodies of some microbats have distinct coworation, dey may be abwe to discriminate cowours.[43][92][93][94]

Megabat species often have eyesight as good as, if not better dan, human vision, uh-hah-hah-hah. Their eyesight is adapted to bof night and daywight vision, incwuding some cowour vision, uh-hah-hah-hah.[94]

Magnetoreception

Microbats make use of magnetoreception, in dat dey have a high sensitivity to de Earf's magnetic fiewd, as birds do. Microbats use a powarity-based compass, meaning dat dey differentiate norf from souf, unwike birds, which use de strengf of de magnetic fiewd to differentiate watitudes, which may be used in wong-distance travew. The mechanism is unknown but may invowve magnetite particwes.[95][96]

Thermoreguwation

Thermographic image of a bat using trapped air as insuwation

Most bats are homeodermic (having a stabwe body temperature), de exception being de vesper bats (Vespertiwionidae), de horseshoe bats (Rhinowophidae), de free-taiwed bats (Mowossidae), and de bent-winged bats (Miniopteridae), which extensivewy use heterodermy (where body temperature can vary).[97] Compared to oder mammaws, bats have a high dermaw conductivity. The wings are fiwwed wif bwood vessews, and wose body heat when extended. At rest, dey may wrap deir wings around demsewves to trap a wayer of warm air. Smawwer bats generawwy have a higher metabowic rate dan warger bats, and so need to consume more food in order to maintain homeodermy.[98]

Bats may avoid fwying during de day to prevent overheating in de sun, since deir dark wing-membranes absorb sowar radiation, uh-hah-hah-hah. Bats may not be abwe to dissipate heat if de ambient temperature is too high;[99] dey use sawiva to coow demsewves in extreme conditions.[47] Among megabats, de fwying fox Pteropus hypomewanus uses sawiva and wing-fanning to coow itsewf whiwe roosting during de hottest part of de day.[100] Among microbats, de Yuma myotis (Myotis yumanensis), de Mexican free-taiwed bat, and de pawwid bat (Antrozous pawwidus) cope wif temperatures up to 45 °C (113 °F) by panting, sawivating, and wicking deir fur to promote evaporative coowing; dis is sufficient to dissipate twice deir metabowic heat production, uh-hah-hah-hah.[101]

Bats awso possess a system of sphincter vawves on de arteriaw side of de vascuwar network dat runs awong de edge of deir wings. When fuwwy open, dese awwow oxygenated bwood to fwow drough de capiwwary network across de wing membrane; when contracted, dey shunt fwow directwy to de veins, bypassing de wing capiwwaries. This awwows bats to controw how much heat is exchanged drough de fwight membrane, awwowing dem to rewease heat during fwight. Many oder mammaws use de capiwwary network in oversized ears for de same purpose.[102]

Torpor

Torpor, a state of decreased activity where de body temperature and metabowism decreases, is especiawwy usefuw for microbats, as dey use a warge amount of energy whiwe active, depend upon an unrewiabwe food source, and have a wimited abiwity to store fat. They generawwy drop deir body temperature in dis state to 6–30 °C (43–86 °F), and may reduce deir energy expenditure by 50 to 99%. Around 97% of aww microbats use torpor.[103] Tropicaw bats may use it to avoid predation, by reducing de amount of time spent on foraging and dus reducing de chance of being caught by a predator.[104] Megabats were generawwy bewieved to be homeodermic, but dree species of smaww megabats, wif a mass of about 50 grams (13⁄4 ounces), have been known to use torpor: de common bwossom bat (Syconycteris austrawis), de wong-tongued nectar bat (Macrogwossus minimus), and de eastern tube-nosed bat (Nyctimene robinsoni). Torpid states wast wonger in de summer for megabats dan in de winter.[105]

During hibernation, bats enter a torpid state and decrease deir body temperature for 99.6% of deir hibernation period; even during periods of arousaw, when dey return deir body temperature to normaw, dey sometimes enter a shawwow torpid state, known as "heterodermic arousaw".[106] Some bats become dormant during higher temperatures to keep coow in de summer monds.[107]

Heterodermic bats during wong migrations may fwy at night and go into a torpid state roosting in de daytime. Unwike migratory birds, which fwy during de day and feed during de night, nocturnaw bats have a confwict between travewwing and eating. The energy saved reduces deir need to feed, and awso decreases de duration of migration, which may prevent dem from spending too much time in unfamiwiar pwaces, and decrease predation, uh-hah-hah-hah. In some species, pregnant individuaws may not use torpor.[108][109]

Size

The smawwest bat is Kitti's hog-nosed bat (Craseonycteris dongwongyai), which is 29–34 mm (11⁄8–13⁄8 in) wong wif a 150-miwwimetre (6 in) wingspan and weighs 2–2.6 g (1⁄16–3⁄32 oz).[110][111] It is awso arguabwy de smawwest extant species of mammaw, next to de Etruscan shrew.[112] The wargest bats are a few species of Pteropus megabats and de giant gowden-crowned fwying fox, (Acerodon jubatus), which can weigh 1.6 kg (31⁄2 wb) wif a wingspan of 1.7 m (5 ft 7 in).[113] Larger bats tend to use wower freqwencies and smawwer bats higher for echowocation; high-freqwency echowocation is better at detecting smawwer prey. Smaww prey may be absent in de diets of warge bats as dey are unabwe to detect dem.[114] The adaptations of a particuwar bat species can directwy infwuence what kinds of prey are avaiwabwe to it.[115]

Ecowogy

Fwight has enabwed bats to become one of de most widewy distributed groups of mammaws.[116] Apart from de high Arctic, de Antarctic and a few isowated oceanic iswands, bats exist in awmost every habitat on Earf.[117] Tropicaw areas tend to have more species dan temperate ones.[118] Different species sewect different habitats during different seasons, ranging from seasides to mountains and deserts, but dey reqwire suitabwe roosts. Bat roosts can be found in howwows, crevices, fowiage, and even human-made structures, and incwude "tents" de bats construct wif weaves.[119] Megabats generawwy roost in trees.[120] Most microbats are nocturnaw[121] and megabats are typicawwy diurnaw or crepuscuwar.[122][123]

In temperate areas, some microbats migrate hundreds of kiwometres to winter hibernation dens;[124] oders pass into torpor in cowd weader, rousing and feeding when warm weader awwows insects to be active.[125] Oders retreat to caves for winter and hibernate for as much as six monds.[125] Microbats rarewy fwy in rain; it interferes wif deir echowocation, and dey are unabwe to hunt.[126]

Food and feeding

Different bat species have different diets, incwuding insects, nectar, powwen, fruit and even vertebrates.[127] Megabats are mostwy fruit, nectar and powwen eaters.[122] Due to deir smaww size, high-metabowism and rapid burning of energy drough fwight, bats must consume warge amounts of food for deir size. Insectivorous bats may eat over 120 percent of deir body weight, whiwe frugivorous bats may eat over twice deir weight.[128] They can travew significant distances each night, exceptionawwy as much as 38.5 km (24 mi) in de spotted bat (Euderma macuwatum), in search of food.[129] Bats use a variety of hunting strategies.[114] Bats get most of deir water from de food dey eat; many species awso drink from water sources wike wakes and streams, fwying over de surface and dipping deir tongues into de water.[130]

The Chiroptera as a whowe are in de process of wosing de abiwity to syndesise vitamin C.[131] In a test of 34 bat species from six major famiwies, incwuding major insect- and fruit-eating bat famiwies, aww were found to have wost de abiwity to syndesise it, and dis woss may derive from a common bat ancestor, as a singwe mutation, uh-hah-hah-hah.[132][b] At weast two species of bat, de frugivorous bat (Rousettus weschenauwtii) and de insectivorous bat (Hipposideros armiger), have retained deir abiwity to produce vitamin C.[133]

Insects

Most microbats, especiawwy in temperate areas, prey on insects.[127] The diet of an insectivorous bat may span many species,[134] incwuding fwies, mosqwitos, beetwes, mods, grasshoppers, crickets, termites, bees, wasps, mayfwies and caddisfwies.[40][135] Large numbers of Mexican free-taiwed bats (Tadarida brasiwiensis) fwy hundreds of metres above de ground in centraw Texas to feed on migrating mods.[136] Species dat hunt insects in fwight, wike de wittwe brown bat (Myotis wucifugus), may catch an insect in mid-air wif de mouf, and eat it in de air or use deir taiw membranes or wings to scoop up de insect and carry it to de mouf.[137][138] The bat may awso take de insect back to its roost and eat it dere.[139] Swower moving bat species such as de brown wong-eared bat (Pwecotus auritus) and many horseshoe bat species, may take or gwean insects from vegetation or hunt dem from perches.[40] Insectivorous bats wiving at high watitudes have to consume prey wif higher energetic vawue dan tropicaw bats.[140]

Fruit and nectar

Fruit eating, or frugivory, is found in bof major suborders. Bats prefer ripe fruit, puwwing it off de trees wif deir teef. They fwy back to deir roosts to eat de fruit, sucking out de juice and spitting de seeds and puwp out onto de ground. This hewps disperse de seeds of dese fruit trees, which may take root and grow where de bats have weft dem, and many species of pwants depend on bats for seed dispersaw.[141][142] The Jamaican fruit bat (Artibeus jamaicensis) has been recorded carrying fruits weighing 3–14 g (1⁄8–1⁄2 oz) or even as much as 50 g (13⁄4 oz).[143]

Nectar-eating bats have acqwired speciawised adaptations. These bats possess wong muzzwes and wong, extensibwe tongues covered in fine bristwes dat aid dem in feeding on particuwar fwowers and pwants.[142][144] The tube-wipped nectar bat (Anoura fistuwata) has de wongest tongue of any mammaw rewative to its body size. This is beneficiaw to dem in terms of powwination and feeding. Their wong, narrow tongues can reach deep into de wong cup shape of some fwowers. When de tongue retracts, it coiws up inside de rib cage.[144] Because of dese features, nectar-feeding bats cannot easiwy turn to oder food sources in times of scarcity, making dem more prone to extinction dan oder types of bat.[145][146] Nectar feeding awso aids a variety of pwants, since dese bats serve as powwinators, as powwen gets attached to deir fur whiwe dey are feeding. Around 500 species of fwowering pwant rewy on bat powwination and dus tend to open deir fwowers at night.[142] Many rainforest pwants depend on bat powwination, uh-hah-hah-hah.[147]

Vertebrates

Some bats prey on oder vertebrates, such as fish, frogs, wizards, birds and mammaws.[40][149] The fringe-wipped bat (Trachops cirrhosus,) for exampwe, is skiwwed at catching frogs. These bats wocate warge groups of frogs by tracking deir mating cawws, den pwucking dem from de surface of de water wif deir sharp canine teef.[150] The greater noctuwe bat can catch birds in fwight.[148] Some species, wike de greater buwwdog bat (Noctiwio weporinus) hunt fish. They use echowocation to detect smaww rippwes on de water's surface, swoop down and use speciawwy enwarged cwaws on deir hind feet to grab de fish, den take deir prey to a feeding roost and consume it.[151] At weast two species of bat are known to feed on oder bats: de spectraw bat (Vampyrum spectrum), and de ghost bat (Macroderma gigas).[152]

Bwood

A few species, specificawwy de common, white-winged, and hairy-wegged vampire bats, onwy feed on animaw bwood (hematophagy). The common vampire bat typicawwy feeds on warge mammaws such as cattwe; de hairy-wegged and white-winged vampires feed on birds.[153] Vampire bats target sweeping prey and can detect deep breading.[154] Heat sensors in de nose hewp dem to detect bwood vessews near de surface of de skin, uh-hah-hah-hah.[155] They pierce de animaw's skin wif deir teef, biting away a smaww fwap,[156] and wap up de bwood wif deir tongues, which have wateraw grooves adapted to dis purpose.[157] The bwood is kept from cwotting by an anticoaguwant in de sawiva.[156]

Predators, parasites, and diseases

Bats are subject to predation from birds of prey, such as owws, hawks, and fawcons, and at roosts from terrestriaw predators abwe to cwimb, such as cats.[158] Twenty species of tropicaw New Worwd snakes are known to capture bats, often waiting at de entrances of refuges, such as caves, for bats to fwy past.[159] J. Rydeww and J. R. Speakman argue dat bats evowved nocturnawity during de earwy and middwe Eocene period to avoid predators.[158] The evidence is dought by some zoowogists to be eqwivocaw so far.[160]

White nose syndrome is a condition associated wif de deads of miwwions of bats in de Eastern United States and Canada.[163] The disease is named after a white fungus, Pseudogymnoascus destructans, found growing on de muzzwes, ears, and wings of affwicted bats. The fungus is mostwy spread from bat to bat, and causes de disease.[164] The fungus was first discovered in centraw New York State in 2006 and spread qwickwy to de entire Eastern US norf of Fworida; mortawity rates of 90–100% have been observed in most affected caves.[165]New Engwand and de mid-Atwantic states have, since 2006, witnessed entire species compwetewy extirpated and oders wif numbers dat have gone from de hundreds of dousands, even miwwions, to a few hundred or wess.[166] Nova Scotia, Quebec, Ontario, and New Brunswick have witnessed identicaw die offs, wif de Canadian government making preparations to protect aww remaining bat popuwations in its territory.[167] Scientific evidence suggests dat wonger winters where de fungus has a wonger period to infect bats resuwt in greater mortawity.[168][169][170] In 2014, de infection crossed de Mississippi River,[171] and in 2017, it was found on bats in Texas.[172]

Bats are naturaw reservoirs for a warge number of zoonoticpadogens,[173] incwuding rabies, endemic in many bat popuwations,[174][175][176]histopwasmosis bof directwy and in guano,[177]Nipah and Hendra viruses,[178][179] and possibwy de ebowa virus,[180][181] whose naturaw reservoir is yet unknown, uh-hah-hah-hah.[182][183] Their high mobiwity, broad distribution, wong wife spans, substantiaw sympatry (range overwap) of species, and sociaw behaviour make bats favourabwe hosts and vectors of disease.[184] Reviews have found different answers as to wheder bats have more zoonotic viruses dan oder mammaw groups. One 2015 review found dat bats, rodents, and primates aww harbored significantwy more zoonotic viruses (which can be transmitted to humans) dan oder mammaw groups, dough de differences among de aforementioned dree groups were not significant (bats have no more zoonotic viruses dan rodents and primates).[185] Anoder 2020 review of mammaws and birds found dat de identify of de taxonomic groups did not have any impact on de probabiwity of harboring zoonotic viruses. Instead, more diverse groups had greater viraw diversity.[186]

They seem to be highwy resistant to many of de padogens dey carry, suggesting a degree of adaptation to deir immune systems.[184]>[187][188] Their interactions wif wivestock and pets, incwuding predation by vampire bats, accidentaw encounters, and de scavenging of bat carcasses, compound de risk of zoonotic transmission, uh-hah-hah-hah.[175] Bats are impwicated in de emergence of severe acute respiratory syndrome (SARS) in China, since dey serve as naturaw hosts for coronaviruses, severaw from a singwe cave in Yunnan, one of which devewoped into de SARS virus.[177][189][190] However, dey do neider cause nor spread Covid-19.[191]

Behaviour and wife history

Sociaw structure

Some bats wead sowitary wives, whiwe oders wive in cowonies of more dan a miwwion, uh-hah-hah-hah.[192] Living in warge cowonies wessens de risk to an individuaw of predation, uh-hah-hah-hah.[40] Temperate bat species may swarm at hibernation sites as autumn approaches. This may serve to introduce young to hibernation sites, signaw reproduction in aduwts and awwow aduwts to breed wif dose from oder groups.[193]

Severaw species have a fission-fusion sociaw structure, where warge numbers of bats congregate in one roosting area, awong wif breaking up and mixing of subgroups. Widin dese societies, bats are abwe to maintain wong-term rewationships.[194] Some of dese rewationships consist of matriwineawwy rewated femawes and deir dependent offspring.[195] Food sharing and mutuaw grooming may occur in certain species, such as de common vampire bat (Desmodus rotundus), and dese strengden sociaw bonds.[196][197]

Communication

Bats are among de most vocaw of mammaws and produce cawws to attract mates, find roost partners and defend resources. These cawws are typicawwy wow-freqwency and can travew wong distances.[40][199] Mexican free-taiwed bats are one of de few species to "sing" wike birds. Mawes sing to attract femawes. Songs have dree phrases: chirps, triwws and buzzes, de former having "A" and "B" sywwabwes. Bat songs are highwy stereotypicaw but wif variation in sywwabwe number, phrase order, and phrase repetitions between individuaws.[198] Among greater spear-nosed bats (Phywwostomus hastatus), femawes produce woud, broadband cawws among deir roost mates to form group cohesion, uh-hah-hah-hah. Cawws differ between roosting groups and may arise from vocaw wearning.[200]

In a study on captive Egyptian fruit bats, 70% of de directed cawws couwd be identified by de researchers as to which individuaw bat made it, and 60% couwd be categorised into four contexts: sqwabbwing over food, jostwing over position in deir sweeping cwuster, protesting over mating attempts and arguing when perched in cwose proximity to each oder. The animaws made swightwy different sounds when communicating wif different individuaw bats, especiawwy dose of de opposite sex.[201] In de highwy sexuawwy dimorphichammer-headed bat (Hypsignadus monstrosus), mawes produce deep, resonating, monotonous cawws to attract femawes. Bats in fwight make vocaw signaws for traffic controw. Greater buwwdog bats honk when on a cowwision course wif each oder.[199]

Bats awso communicate by oder means. Mawe wittwe yewwow-shouwdered bats (Sturnira wiwium) have shouwder gwands dat produce a spicy odour during de breeding season, uh-hah-hah-hah. Like many oder species, dey have hair speciawised for retaining and dispersing secretions. Such hair forms a conspicuous cowwar around de necks of de some Owd Worwd megabat mawes. Mawe greater sac-winged bats (Saccopteryx biwineata) have sacs in deir wings in which dey mix body secretions wike sawiva and urine to create a perfume dat dey sprinkwe on roost sites, a behaviour known as "sawting". Sawting may be accompanied by singing.[199]

Reproduction and wifecycwe

Group of powygynous vampire bats

Most bat species are powygynous, where mawes mate wif muwtipwe femawes. Mawe pipistrewwe, noctuwe and vampire bats may cwaim and defend resources dat attract femawes, such as roost sites, and mate wif dose femawes. Mawes unabwe to cwaim a site are forced to wive on de periphery where dey have wess reproductive success.[202][40]Promiscuity, where bof sexes mate wif muwtipwe partners, exists in species wike de Mexican free-taiwed bat and de wittwe brown bat.[203][204] There appears to be bias towards certain mawes among femawes in dese bats.[40] In a few species, such as de yewwow-winged bat and spectraw bat, aduwt mawes and femawes form monogamous pairs.[40][205]Lek mating, where mawes aggregate and compete for femawe choice drough dispway, is rare in bats[206] but occurs in de hammerheaded bat.[207]

For temperate wiving bats, mating takes pwace in wate summer and earwy autumn, uh-hah-hah-hah.[208] Tropicaw bats may mate during de dry season, uh-hah-hah-hah.[209] After copuwation, de mawe may weave behind a mating pwug to bwock de sperm of oder mawes and dus ensure his paternity.[210] In hibernating species, mawes are known to mate wif femawes in torpor.[40] Femawe bats use a variety of strategies to controw de timing of pregnancy and de birf of young, to make dewivery coincide wif maximum food abiwity and oder ecowogicaw factors. Femawes of some species have dewayed fertiwisation, in which sperm is stored in de reproductive tract for severaw monds after mating. Mating occurs in de autumn but fertiwisation does not occur untiw de fowwowing spring. Oder species exhibit dewayed impwantation, in which de egg is fertiwised after mating, but remains free in de reproductive tract untiw externaw conditions become favourabwe for giving birf and caring for de offspring.[211] In anoder strategy, fertiwisation and impwantation bof occur, but devewopment of de foetus is dewayed untiw good conditions prevaiw. During de dewayed devewopment de moder keeps de fertiwised egg awive wif nutrients. This process can go on for a wong period, because of de advanced gas exchange system.[212]

Newborn common pipistrewwe, Pipistrewwus pipistrewwus

For temperate wiving bats, birds typicawwy take pwace in May or June in de nordern hemisphere; birds in de soudern hemisphere occur in November and December. Tropicaw species give birf at de beginning of de rainy season, uh-hah-hah-hah.[213] In most bat species, femawes carry and give birf to a singwe pup per witter.[214] At birf, a bat pup can be up to 40 percent of de moder's weight,[40] and de pewvic girdwe of de femawe can expand during birf as de two hawves are connected by a fwexibwe wigament.[215] Femawes typicawwy give birf in a head-up or horizontaw position, using gravity to make birding easier. The young emerges rear-first, possibwy to prevent de wings from getting tangwed, and de femawe cradwes it in her wing and taiw membranes. In many species, femawes give birf and raise deir young in maternity cowonies and may assist each oder in birding.[216][217][215]

Most of de care for a young bat comes from de moder. In monogamous species, de fader pways a rowe. Awwo-suckwing, where a femawe suckwes anoder moder's young, occurs in severaw species. This may serve to increase cowony size in species where femawes return to deir nataw cowony to breed.[40] A young bat's abiwity to fwy coincides wif de devewopment of an aduwt body and forewimb wengf. For de wittwe brown bat, dis occurs about eighteen days after birf. Weaning of young for most species takes pwace in under eighty days. The common vampire bat nurses its offspring beyond dat and young vampire bats achieve independence water in wife dan oder species. This is probabwy due to de species' bwood-based diet, which is difficuwt to obtain on a nightwy basis.[218]

Life expectancy

The maximum wifespan of bats is dree-and-a-hawf times wonger dan oder mammaws of simiwar size. Six species have been recorded to wive over 30 years in de wiwd: de brown wong-eared bat (Pwecotus auritus), de wittwe brown bat (Myotis wucifugus), Brandt's bat (Myotis brandti), de wesser mouse-eared bat (Myotis bwydii) de greater horseshoe bat (Rhinowophus ferrumeqwinum), and de Indian fwying fox (Pteropus giganteus).[219] One hypodesis consistent wif de rate-of-wiving deory winks dis to de fact dat dey swow down deir metabowic rate whiwe hibernating; bats dat hibernate, on average, have a wonger wifespan dan bats dat do not.[220][221] Anoder hypodesis is dat fwying has reduced deir mortawity rate, which wouwd awso be true for birds and gwiding mammaws. Bat species dat give birf to muwtipwe pups generawwy have a shorter wifespan dan species dat give birf to onwy a singwe pup. Cave-roosting species may have a wonger wifespan dan non-roosting species because of de decreased predation in caves. A mawe Brandt's bat was recaptured in de wiwd after 41 years, making it de owdest known bat.[221][222]

Many peopwe put up bat houses to attract bats.[228] The 1991 University of Fworida bat house is de wargest occupied artificiaw roost in de worwd, wif around 400,000 residents.[229] In Britain, dickwawwed and partwy underground Worwd War II piwwboxes have been converted to make roosts for bats,[230][231] and purpose-buiwt bat houses are occasionawwy buiwt to mitigate damage to habitat from road or oder devewopments.[232][233]Cave gates are sometimes instawwed to wimit human entry into caves wif sensitive or endangered bat species. The gates are designed not to wimit de airfwow, and dus to maintain de cave's micro-ecosystem.[234] Of de 47 species of bats found in de United States, 35 are known to use human structures, incwuding buiwdings and bridges. Fourteen species use bat houses.[235]

Bats are eaten in countries across Africa, Asia and de Pacific Rim. In some cases, such as in Guam, fwying foxes have become endangered drough being hunted for food.[236] There is evidence dat wind turbines create sufficient barotrauma (pressure damage) to kiww bats.[237] Bats have typicaw mammawian wungs, which are dought to be more sensitive to sudden air pressure changes dan de wungs of birds, making dem more wiabwe to fataw rupture.[238][239][240][241][242] Bats may be attracted to turbines, perhaps seeking roosts, increasing de deaf rate.[238] Acoustic deterrents may hewp to reduce bat mortawity at wind farms.[243]

Cuwturaw significance

Since bats are mammaws, yet can fwy, dey are considered to be wiminaw beings in various traditions.[244] In many cuwtures, incwuding in Europe, bats are associated wif darkness, deaf, witchcraft, and mawevowence.[245] Among Native Americans such as de Creek, Cherokee and Apache, de bat is a trickster spirit. In Tanzania, a winged batwike creature known as Popobawa is bewieved to be a shapeshifting eviw spirit dat assauwts and sodomises its victims.[246] In Aztecmydowogy, bats symbowised de wand of de dead, destruction, and decay.[247][248][249] An East Nigerian tawe tewws dat de bat devewoped its nocturnaw habits after causing de deaf of his partner, de bush-rat, and now hides by day to avoid arrest.[250]

More positive depictions of bats exist in some cuwtures. In China, bats have been associated wif happiness, joy and good fortune. Five bats are used to symbowise de "Five Bwessings": wongevity, weawf, heawf, wove of virtue and peacefuw deaf.[251] The bat is sacred in Tonga and is often considered de physicaw manifestation of a separabwe souw.[252] In de Zapotec civiwisation of Mesoamerica, de bat god presided over corn and fertiwity.[253]

Economics

Insectivorous bats in particuwar are especiawwy hewpfuw to farmers, as dey controw popuwations of agricuwturaw pests and reduce de need to use pesticides. It has been estimated dat bats save de agricuwturaw industry of de United States anywhere from $3.7 biwwion to $53 biwwion per year in pesticides and damage to crops. This awso prevents de overuse of pesticides, which can powwute de surrounding environment, and may wead to resistance in future generations of insects.[263]

The Congress Avenue Bridge in Austin, Texas, is de summer home to Norf America's wargest urban bat cowony, an estimated 1,500,000 Mexican free-taiwed bats. About 100,000 tourists a year visit de bridge at twiwight to watch de bats weave de roost.[266]

^Jones, T. W. (1852). "Discovery That de Veins of de Bat's Wing (Which are Furnished wif Vawves) are Endowed wif Rydmicaw Contractiwity, and That de Onward Fwow of Bwood is Accewerated by Each Contraction". Phiwosophicaw Transactions of de Royaw Society of London. 142: 131–136. doi:10.1098/rstw.1852.0011. JSTOR108539.

^ abChamberwain, T. (6 December 2006). "Photo in de News: Bat Has Longest Tongue of Any Mammaw". Nationaw Geographic News. Nationaw Geographic Society. Archived from de originaw on 6 June 2007. Retrieved 18 June 2007. A. fistuwata (shown wapping sugar water from a tube) has de wongest tongue, rewative to body wengf, of any mammaw—and now scientists dink dey know why

^Choi, C. Q. (2006). "Going to Bat". Scientific American. pp. 24, 26. Long known as vectors for rabies, bats may be de origin of some of de most deadwy emerging viruses, incwuding SARS, Ebowa, Nipah, Hendra and Marburg. Note: This is a way summary of de various scientific pubwications cited in de preceding sentence.

^Oppew, K. "The Characters: Shade". Kennef Oppew. Archived from de originaw on 26 September 2017. Retrieved 25 September 2017. "Shade is based on a Siwver-Haired Bat. I dought dey were very dashing-wooking creatures. I wiked de fact dis was a bat dat wived in de same part of de worwd as me (eastern Canada). These are smaww creatures, wif a wing span of a few inches. Their bodies are about de same size as mice. They're insectivores, which means dey eat onwy insects." – K.O.